The present invention relates to a plastic working method and an apparatus therefor, and more particularly to a method and an apparatus wherein a swivel motion of a die and a reciprocating motion of the die against a workpiece are combined with each other to thereby further increase fluidity of material of the workpiece to thus enhance the filing property of the material to the die.
In a so-called rotary forging in which a upper die having a predetermined inclination angle relative to a workpiece is swiveled to perform a plastic working, only one of a swivel motion at a predetermined inclination angle and a swing motion in a predetermined inclination angle range has been conventionally applied to the upper die.
Not only in a rotary forging work but also a general forging work, it is very important to enhance fluidity of material of the workpiece and to enhance the filing rate of the material into the lower die supporting the workpiece thereon.
However, in the conventional rotary forging work, since only the plastic working is performed to the workpiece by the swivel motion at the predetermined inclination angle or by the swing motion in the predetermined inclination angle range as described above, although the material of the workpiece is spread in a flat manner, the filing of the material into the lower die is not satisfactory. In particular, in a case of forging a workpiece so as to provide a projection in the middle or intermediate portion of the final product, there is a problem that the filing of the material would be insufficient and a material lacking or insufficient spreading may locally occur. Incidentally, a commonly assigned copending U.S. Pat. Application Ser. No. 07/227,301 has been filed on Aug. 2, 1988 (corresponding to European Patent Application No. 88307331.4 filed on Aug. 8, 1988).